JPH03234852A - absorbent articles - Google Patents

Abstract

PURPOSE:To obtain a disposable absorbent article, using a nonwoven fabric, excellent in absorptivity of high viscosity menstrual blood, high viscosity humor, etc., and good in touch to the skin by employing the nonwoven fabric having specific pores, a state of nonperforated parts, pore area, opening ratio, strength, etc., as a surface material. CONSTITUTION:The objective article obtained by using a nonwoven fabric having many pores in at least a permeating part of excreted liquid, >=60mu average distance between fibers in nonperforated parts, 1.5-20mm<2>/pore area, 5-50% opening ratio and >=0.8g.cm<3> ratio (f*) of the nonwoven fabric strength to the density of the number of fibers expressed by the formula [F is the tenacity (g) in the direction perpendicular to the fiber orientation of the nonwoven fabric; V is the volume (cm<3>) of the nonwoven fabric; N is the number of fibers in the nonwoven fabric] and a nearly uniform density of bonded points of the nonperforated parts as a surface material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to disposable absorbent articles, particularly absorbent articles such as sanitary napkins, postpartum napkins, paper diapers, and cosmetic cotton. More specifically, it is a disposable fabric made of non-woven fabric that has excellent absorbency for body fluids, particularly highly viscous body fluids such as highly viscous menstrual blood and diarrhea, or highly viscous fluids such as cosmetic facial cleansing creams, and has an excellent feel on the skin. The present invention relates to possible absorbent articles.

[Prior Art and Problems to be Solved by the Invention] Conventional absorbent articles, such as sanitary napkins, disposable diapers, or cosmetic cotton, generally have an absorbent layer made of a cotton-like valve, absorbent paper, etc., and if necessary, the lower surface and It consists of a leak-proof layer placed on the sides and a nonwoven fabric placed on the surface.

The nonwoven fabric that forms the surface layer of such absorbent articles includes
A variety of performance is required, but in particular, from low viscosity liquids such as normal blood and urine to highly viscous menstrual blood discharged during menstruation, diarrhea stool, and solid content such as cosmetic facial cream. For liquids with a wide range of properties, including highly viscous liquids with dispersed substances, we need to suppress the flow of liquid on the surface (referred to as liquid flow) that can lead to leakage, feel good on the skin, and cover the absorbent layer. The most desired performance is good properties (moderate strength, no fluff, shielding properties).

In recent years, with the rapid spread of synthetic fiber-based dry non-woven fabrics and technological improvements, we believe that these performance requirements are met to a large extent for low-viscosity liquids such as normal blood, urine, and lotions. It will be done.

Incidentally, during actual menstruation, highly viscous menstrual blood containing intrauterine mucosa, lochia, etc. is often discharged, and highly viscous liquid such as diarrheal stool may also be discharged during excretion. Furthermore, even in cosmetics, it is often necessary to process highly viscous dispersion systems, such as facial cleansing creams.

Nonwoven fabrics designed to absorb such highly viscous liquids have not yet been sufficiently studied.

In the reports made so far, the distance between fibers of nonwoven fabric is increased (Japanese Patent Laid-Open No. 62-181041), and macroscopic holes are installed in the surface material (Japanese Patent Laid-Open No. 62-125001).
(No., Japanese Patent Application Laid-Open No. 62-125061) The idea of fortune-telling was a typical example. However, these surface materials are designed with too much emphasis on the absorption function, and therefore do not meet the more basic requirements of a surface material, such as the feel when it comes in contact with the skin, and the coverage of the absorbent layer ( There are many points that need to be improved in terms of appropriate strength, no fluff, and shielding properties, so it cannot be said that it has yet reached a practical level.

In other words, in nonwoven fabrics obtained by conventional manufacturing techniques,
It has been extremely difficult to simultaneously satisfy the absorbency of highly viscous liquids and the strength and texture that are appropriate for practical use.

Therefore, the object of the present invention is to obtain a nonwoven fabric that has the disadvantages of conventional nonwoven fabrics and satisfies the following three conditions.

■ At least in the state of a fiber web, the fibers should be loosely intertwined and have sufficient distance between the fibers.

■ Maintain the fiber web morphology (loosely intertwined, large distances between fibers) as much as possible to achieve fixation of fibers that provides appropriate strength and texture.

■ It satisfies the basic requirements (■) and (2) for nonwoven fabrics listed above, and has appropriate pores through which high-viscosity liquids can quickly permeate.

■ and ■ are largely due to the manufacturing technology of the nonwoven fabric base, and ■ is largely due to the hole opening technology of the nonwoven fabric.

Therefore, first, regarding the conventional nonwoven fabric, the above conditions ■, ■
In order to clarify the problems with non-woven fabrics,
They are classified into three categories and are explained in detail below along with the technical background.

A. Nonwoven fabric created by entanglement of fiber stables (entangled nonwoven fabric): A fibrous web formed from a card can be obtained by needling with a high-speed fluid (water, air, etc.) or a needle. “Waterjet Nonwoven Fabric J” is compatible with the needling method.

It is called "needle punch nonwoven fabric".

B. Nonwoven fabric in which fibers are bonded together by thermal melting of a constituent resin (thermally bonded nonwoven fabric): This is further classified as follows.

B-1, a type in which fiber filaments with almost no crimp are thermally bonded and the bonded area is macroscopically discontinuously distributed. It can be obtained by laminating fibers while spinning to form a web, and fusing and fixing the fibers together with a pinpoint top-1 embossing. Generally called "spunbond nonwoven fabric."

B-2, the degree of adhesive melting between fiber stables is large;
A type in which the bonding points are tightly and irregularly distributed. It can be obtained by compressing a fibrous web formed by a card at a temperature higher than the melting point of the fibers and using a heat roller to bond the fibers together. Generally called "heat roll bonded nonwoven fabric."

B-3, type in which only the contact points of the fiber stables are melted and bonded, and the bonding point density is small and irregularly distributed. It is obtained by passing hot air at a temperature higher than the melting point of the fibers through a fibrous web formed of card to bond the fibers together. Generally, it is called "suction heat bond nonwoven fabric."

C9 A nonwoven fabric in which fiber stables are bonded to each other by a chemical binder, and the bonding points are tightly and irregularly distributed, or regularly and discontinuously: A fiber web formed by a card is bonded to a chemical binder. It can be obtained by immersing it in a solution or by coating it with an indica film using a roll coater. It is generally called a "binder-type nonwoven fabric."

Next, the problems with the above nonwoven fabrics will be discussed.

Spunbond nonwoven fabrics can essentially only achieve very small interfiber distances for condition (3).

This is because in a spunbond nonwoven fabric, there is almost no crimp in the fibers, and since the filaments are laminated, the fibers cannot intertwine with each other three-dimensionally, making it impossible to increase the bulk of the fiber web.

Furthermore, since the bonding points between fibers are macroscopically discontinuously distributed, fuzzing tends to occur, and if the density of bonding points is increased to a level that prevents fuzzing, the entire nonwoven fabric becomes hard. In this type of nonwoven fabric, the maximum distance between fibers is about 40μ.

Entangled nonwoven fabrics, heat roll bonded nonwoven fabrics, and binder type nonwoven fabrics are very disadvantageous to condition (3).

In entangled nonwoven fabrics, it is inherently difficult to maintain the loose entanglement of the initial fibrous stable web, since the nonwoven fabric cannot be given adequate strength unless the fibers are tightly entangled.

In order to increase the distance between fibers even if the entanglement is tight, the thickness of the fibers (
It is effective to increase the fineness (fineness), but increasing the fineness significantly reduces the strength of the nonwoven fabric in the case of entangled nonwoven fabrics. Also,
Another factor that makes it difficult to put the entangled nonwoven fabric into practical use is that the amount of fuzz shedding due to friction on the surface of the nonwoven fabric caused by the movement of the wearer of the absorbent article is the largest among the five types.

Since the fibers of the heat roll bonded nonwoven fabric are melted and bonded under pressure heat, the distance between the fibers is significantly lower than that of a fibrous web. Furthermore, since heat is conducted from the heat roller through the fiber resin, the adhesion efficiency is poor, and the degree of non-uniformity of adhesion between the surface and inside of the nonwoven fabric is large, making it difficult to balance the strength and texture of the nonwoven fabric.

In binder-type nonwoven fabrics, the binder is distributed not only at the contact points between fibers, but also in the spaces between the fibers.
The bonding points become very tight, resulting in small interfiber distances.

As mentioned above, it is currently extremely difficult to make the distance between fibers 40 μ or more for entangled nonwoven fabrics, heat roll bonded nonwoven fabrics, and binder type nonwoven fabrics, and it is difficult to satisfy condition (2).

Suction heat bonded nonwoven fabric has great potential in that it simultaneously satisfies conditions (2) and (2). That is, suction heat-bonded nonwoven fabrics generally use a fiber stable web formed by cards, so the distance between the fibers can be increased in principle, and since heat is conducted by air fluid passing through the nonwoven fabric, the distance between the fibers can be increased. High fixation efficiency,
Easy to balance strength and texture.

However, in reality, the density of bonding points is lower than that of other nonwoven fabrics, so in order to obtain an appropriate strength for practical use, the fineness has to be lowered (as a result, it is difficult to increase the distance between fibers). .

Next, in order to clarify the problem with the above-mentioned condition (2) regarding conventional nonwoven fabrics, two typical types of perforation techniques will be described in detail below along with the technical background.

(2) A method in which a nonwoven fabric web is placed on a perforated net, a high-speed water jet is sprayed onto the web, and the web resting on the non-porous portion of the net is twisted to form holes.

This is the same principle as the method for manufacturing water jet nonwoven fabrics, and the fibers in non-porous areas are inevitably entangled. Industrially, waterjet nonwoven fabrics, including Sontara (DuPont), are often simultaneously manufactured as perforated nonwoven fabrics.

The holes created by this method have a relatively clear outline and a good texture. However, as mentioned above, since the non-porous portions are entangled, the disadvantages associated with waterjet nonwoven fabrics (small distance between fibers in the non-porous portions, fluffing) occur, and the effect of the pores on soft stool absorption is reduced. Significant decline. In addition, with this method, the hydrophilic agent on the fiber surface that constitutes the non-porous part falls off, and the surface of the nonwoven fabric becomes extremely water-repellent, especially in structures that are mainly made of synthetic fibers, and it has not only soft stool permeability but also normal low viscosity. The rate of liquid absorption is also significantly reduced. Also, this method
It is extremely difficult to open pores in thermally bonded nonwoven fabrics or spunbond nonwoven fabrics that have a strong bond between fibers, and the resulting nonwoven fabric is mostly water-resistant. It has the disadvantage of being limited to jet nonwoven fabrics.

■ Method of punching holes in non-woven fabric with a heat pin.

This method is a technique that has been known for a long time since it is possible to provide holes in nonwoven fabrics other than entangled nonwoven fabrics.

However, this method also has many drawbacks as shown below before it can be put into practical use.

(i) The hole cannot be fixed simply by piercing it with a heat pin, so in many cases the temperature of the pin is set higher than the melting point of the constituent fibers of the nonwoven fabric and the hole is made while melting the fibers, resulting in hard firmness around the hole. , the texture of the surface of the nonwoven fabric is significantly reduced. On the other hand, if the temperature of the heat pin is lower than the melting point of the constituent fibers of the nonwoven fabric, the separated fibers will recover after the pin is removed, and the pores will become smaller, or in the worst case, the pores will become smaller. disappear, and as a result, many of the fabrics have pores so small that they cannot be called porous nonwoven fabrics.

(ii) To prevent the above drawbacks, mix low-melting point fibers into the nonwoven fabric, make the holes with the pin temperature slightly below the melting point of the fibers, and set the low-melting point fibers at the same time to create a hole around the hole. There are also some tricks to restore the fibers. However, in the nonwoven fabric produced by this method, the non-porous area around the pores is compressed and fixed.
The distance between fibers is significantly reduced. As the porosity increases and the area of the non-porous portion becomes narrower, the proportion occupied by the compressed portion increases and this problem becomes more severe. In addition, in order to fully exhibit the setting effect, the proportion of low-melting point fibers must be increased, which results in hardness around the holes and a decrease in the texture of the surface material.

As mentioned above, there is no conventional nonwoven fabric that simultaneously satisfies the distance between fibers that is sufficient to make effective use of the pores that allow high viscosity liquids to pass through, and the strength and texture that are appropriate for practical use. The absorbent article aimed at by the present invention could not be obtained.

[Means to solve the problem]

The present inventors have conducted extensive research to improve the drawbacks of nonwoven fabrics used as surface materials for conventional absorbent articles. It has excellent permeability to highly viscous liquids such as blood, diarrheal stool, and cosmetic facial cleansing cream, feels good when it comes in contact with the skin, and has good covering properties for the absorbent layer (moderate strength, no fluff, shielding properties). We have discovered a good surface material for absorbent articles and completed the present invention.

That is, the present invention provides an absorbent article characterized by using, as a surface material, a nonwoven fabric that satisfies all of the conditions shown in (1) to (6) below.

(1) At least the excretory liquid permeable portion has a large number of holes.

(2) The average interfiber distance in the non-pore portion is 60μ or more.

(3) Nonwoven fabric strength and fiber 4 shown by the following formula (1) The ratio f'' to the number density is 0.8 g-cm3 or more.

F (In the formula, F: Tensile strength in the direction perpendicular to the fiber orientation of the nonwoven fabric (g) C: Tenacity of the nonwoven fabric (g) N: Indicates the number of fibers in the nonwoven fabric.) (4) The average pore area is 1.5 to 20 mm2. / pieces.

(4) The pore area is 5 to 50%.

(6) The bonding point density in the non-porous portion is almost uniform.

The most important thing to improve the high viscosity liquid permeability of absorbent articles is the fibrous material contained in the high viscosity liquid,
This means that undigested substances, fine particles, etc. can quickly permeate into the absorbent layer without clogging the fibers that make up the nonwoven fabric.

To this end, it is necessary to have a large number of interfiber voids that are large enough for fibrous materials, undigested materials, fine particles, and the like. The concept of establishing macroscopic pores as regions with large interfiber voids is known. However, the permeation of highly viscous liquids through nonwoven fabrics cannot be solved simply by providing holes. This is because it largely depends on the structure of the non-porous portion. That is, if the distance between the fibers in the non-porous portion is small, the highly viscous liquid will clog the non-porous portion and will not pass through at all, so that it will concentrate and flow into the pore portion. In order to realize efficient permeation of such a large amount of high viscosity liquid, the pores must be made very large, which greatly impairs the coverage as a surface material. Therefore, in order for the pores to function effectively, the permeability of high viscosity liquid is required even in the non-pore portions. Due to the high viscous liquid permeability in this non-porous area, viscous liquids with a high moisture content such as lochia and diarrheal stools efficiently transfer to the absorbent body, greatly reducing the concentration of excreted liquid flowing into the pore area. can do. As a measure of the interfiber voids, the average interfiber distance Δ, which will be described later, can be taken, and the larger Δ in the non-pore portion, the higher the permeability of high viscosity liquids. in particular,
If the average interfiber distance Δ in the non-porous portion of the nonwoven fabric is 60μ or more, it will flow not only in a highly viscous gel-like liquid such as lochia but also in a dispersion system with a very high moisture content such as diarrheal stool. It was found that excretory fluid, which is easily clogged, permeates through the hole well and intensive flow into the pores is reduced.

Furthermore, for a large amount of excretory fluid such as diarrheal stool from an elderly baby, it is preferable that Δ is 120μ or more.
In order to maintain permeability more stably, it is most desirable that Δ be 150 μ or more.

In addition, if the permeability to high viscosity liquids is not inhibited,
There may be a portion where the microscopic average interfiber distance is 60 μm or less due to embossing treatment using heat or ultrasonic waves for the purpose of supplementing strength or adding a pattern as a design.

Here, the average interfiber distance Δ is defined. As a first approximation to the structure of a nonwoven fabric, consider a model in which all fibers are arranged in parallel at equal distances, and the distance between the fibers is called the "average interfiber distance."
shall be.

nH, 1H=(Wα+/100) (1/aid+)
Therefore, .

If the fineness of the fiber i and the basis weight of the nonwoven fabric are Di denier and l11g/po, respectively, w=IQ/s/10000, D+-900000
When substituting aid + these into formula (II) and performing a large deformation, 7. By distributing pores in a nonwoven fabric with a sufficient distance between fibers, it is possible to absorb low-moisture substances such as highly viscous menstrual blood and loose stools. The permeability of high viscosity liquids is most effectively achieved. In order to promote the permeation of high viscosity liquids with low moisture content, the area of each pore must be at least 1.5 mm, and the larger the pore area, the greater the effect. It is preferable not to exceed 20mm2 as the absorbent layer may come into direct contact with the skin, leading to a reduction in the usable range.If the distance between fibers in the non-porous part is 60μ or more, the porosity is 5% or more. When , it is effective for permeation of high viscosity liquid with low moisture content, and this effect is also greater as the porosity increases.

However, if the porosity is too large, the strength of the entire nonwoven fabric will decrease, so it is desirable that the porosity does not exceed 50%.

With the non-porous part and the perforated part having the above structure,
In order to simultaneously provide the nonwoven fabric with appropriate strength, no shedding/fluffing, and pores with a good texture, the present inventors were able to control the inter-fiber distance in the widest range of any existing technology, and the air fluid We focused on suction heat bonded nonwoven fabrics that can form pores by passing through them.

In suction heat bonded nonwoven fabrics, increasing the fineness is very effective in increasing the distance between fibers, but conventionally, this has had the disadvantage of simultaneously decreasing strength. This is because the number of bonding points between fibers decreases as the number of fibers decreases due to higher fineness. Therefore, in order not to reduce the strength even when the fineness is increased, it is necessary to improve the adhesive strength between fibers. The fibers (4 binder fibers) used as molten fibers in suction heat bonded nonwoven fabrics have at least two phases: a low melting point component that melts with hot air and a high melting point component that maintains the crimped form of the fibers without melting. If so, it must have a sheath-core (the core is a high melting point component), side-high-side type). Among these, it is the low melting point component that controls the strength of the nonwoven fabric.

Therefore, as this low melting point component, a polyethylene resin which has a strong adhesive force between the binder fibers after heat melting and whose resin itself is 90 soft was selected, and the molecular weight was set high in order to further increase the adhesive force. Melt flow rate (MFR) was used as the measure, and a polyethylene resin with the lowest possible MFR (<10) was selected. Furthermore, the proportion of low melting point components in the binder fibers was increased as much as possible (the fiber morphology after thermal melting could be maintained) (cross-sectional area ratio of 55% or more).

As a result of constructing a fibrous web using such binder fibers and manufacturing a nonwoven fabric by a suction heat bonding method, it was found that a nonwoven fabric having an inter-fiber distance of 60 μm or more and sufficient nonwoven strength was obtained.

The hole-opening method using the suction heat bond method is basically the same as the water jet method. For example, a fibrous web is placed on a perforated plate corresponding to the pore size and porosity, and hot air slightly lower than the melting point of the fibers is passed through the web to form pores by twisting and heat setting the fibers. Immediately after that, hot air at a temperature higher than the melting point of the fibers is passed through to simultaneously bond the fibers together and stabilize the pore shape.

In this way, holes with a good texture as described below can be formed.

(a) The entire fiber form does not melt around the hole (only the resin near the contact point between the fibers is melted and bonded).

(b) The entire non-porous region has a substantially uniform interfiber adhesion point density (the periphery of the pores is not compressed).

Now, the present inventors adopted a formula as shown in the following formula (1) in order to specify the balance between the strength F of the nonwoven fabric and the inter-fiber distance Δ in the non-porous portion.

(In the formula, F: Tensile strength in the direction perpendicular to the fiber orientation of the nonwoven fabric (g) V: Tensile strength of the nonwoven fabric (g) N: Indicates the number of fibers in the nonwoven fabric.) That is, the tenacity F in the direction perpendicular to the fiber orientation of the nonwoven fabric. The ratio f''2 of N/V and the fiber number density ratio of the non-porous portion is taken as a measure of the high strength/high fiber distance nonwoven fabric.

Equation (I) shows that fl is thick (the more the fiber distance is large (the fiber density is small) and the strength is large.

Nonwoven fabrics generally have fibers oriented in the direction of the production line, so
The strength in the direction perpendicular to the fiber orientation is smaller than that in the fiber orientation direction. Therefore, as the nonwoven fabric strength, we adopted a more practical strength in the direction perpendicular to the fiber orientation.

The method for deriving equation (T) is shown below.

f″ − N/ν If the fineness of the fiber i and the basis weight of the nonwoven fabric are Di (denier) and w (g/no), then w = H/ S /
10000.

Dz =900000aidH By substituting these into the formula (I[[) and performing a large transformation, V
=SL, and therefore.

The present inventors manufactured suction heat bonded nonwoven fabrics using the above-mentioned high-density, strongly adhesive binder fibers with varying strength and inter-fiber distance. When comparing the relationship with conventional nonwoven fabrics for absorbent articles, it was found that the larger f* is, the better the body permeability of high viscosity liquids3 4 is, and the better the covering properties (moderate strength, no fuzz room). Specifically, to achieve the objectives of the present invention, fl is at least 0.8 g-c
Requires m3 or more. In order to further maintain stable nonwoven fabric strength and high inter-fiber distance, preferably 1.2 g.
-It is good to have more than cm3.

The method of manufacturing the nonwoven fabric of the present invention is not limited.

At the current technological level, it is difficult to produce nonwoven fabrics with f''≧0.8 using methods other than the suction heat bonding method, but with future technological advances, it is possible to produce nonwoven fabrics using only entanglement or filament fibers. If a nonwoven fabric satisfying f''≧0.8 can be produced, the same effects as described in the present invention will be exhibited.

Here, in particular, details will be described in the case where the nonwoven fabric of the present invention is manufactured by the sacsibon heat pound method. The basic requirements for the fiber composition of nonwoven fabrics are that the surface is melted by hot air, the crimped structure of the entire fiber is difficult to change, and that it contains thermobonding binder (thermoplastic) fibers made of resin that has strong thermal adhesion between fibers. It is. Typical examples of such fibers include
Polyolefins such as polypropylene and polyethylene,
A sheath made of resins with relatively high and low melting points, such as polyester, polyamides such as nylon 6 and nylon 66, and polyacrylonitrile.
Core type, skin-core type (core made of high melting point resin),
Examples include side-by-side type composite fibers. More preferred among these is a composite fiber in which polyethylene, which has a strong melt adhesion between resins and is soft in itself, is used as a low melting point resin. Most preferred are composite fibers made of combinations of polyethylene-polypropylene and polyethylene-polyester, which have a highly stable crimp elasticity. In addition, to further increase the adhesive strength, it is possible to increase the proportion of low melting point resin in each fiber, but if it is too large, the crimped form of the fiber after heat treatment will become unstable, so it should not exceed 80%. It is desirable that In addition, in the case of binder fibers in which the low melting point resin is polyethylene, the lower the fluidity of the polyethylene resin during heat melting, the stronger the adhesive force will be and the less deformation of the bonding point (good texture). It is desirable for purposes of this invention to use a polyethylene resin of 10 or less. Furthermore, in a highly compatible combination of low melting point resin/high melting point resin, the adhesion between the binder fibers is high. For example, when polyethylene resin is used as the low melting point resin, polypropylene is used as the high melting point resin, It is effective to use a resin obtained by blending a polyethylene resin with a high elastic resin such as the above.

The blending ratio of binder fibers and non-binder fibers can be set arbitrarily as long as the finished nonwoven fabric satisfies f''≧0.8.However, at present, paper diapers that require high strength and high anti-fluff properties For applications, the blending ratio of binder fibers is preferably 70% or more, and most preferably 100%.
It is a certain thing. For sanitary napkins and cosmetic cotton applications where texture is more important, the blending rate of binder fiber should be at least 50%.
It's good to have. By dividing the nonwoven fabric layer into a layer that imparts strength and a layer that imparts texture/bulk functions, it is possible to efficiently develop the functions of the intended absorbent article. Specifically, ■ For sanitary napkin applications/cosmetic surface applications, the blending ratio of binder fibers should be at least 70% of the layer that imparts strength;
In the layer imparting texture/bulk, it is effective to increase the blending rate of non-binder fibers to 40% or more.

■ For disposable diaper applications, the layer that imparts strength should mainly contain binder fibers with a high fineness that does not deteriorate the texture, and the layer that imparts texture/bulk should mainly contain fibers with a relatively larger fineness than the layer that imparts strength. is valid.

Since the nonwoven fabric becomes more fluffy as the blending ratio of non-binder fibers increases, it is preferable that the blending ratio of these fibers is 50% or less in each layer of the nonwoven fabric. Since polyethylene-based Hainter fibers and polypropylene fibers, and amorphous polyester-based binder fibers and polyester fibers are highly compatible, 7 8 In a nonwoven fabric layer in which these are mixed, fluff can be removed if the binder fiber blend ratio is 30%. prevention can be achieved.

In order to increase the distance between fibers of a nonwoven fabric, the crimp form of the fibers is also important. The above-mentioned binder fibers or non-binder fibers that have some kind of pilateral structure and are given three-dimensional crimps form a web of the same weight compared to those that are given only normal mechanical crimps by stuffing bonks, etc. It is more preferable in that the inter-fiber voids are large and the texture is good.

The thickness of the fibers can be freely selected as long as it is sufficiently smaller than the average interfiber distance, which is defined as 60 μm or more, and as a guideline, it is preferably 15% or less of the average interfiber distance. However, in consideration of the strength and texture of the nonwoven fabric, it is desirable that the denier does not exceed 10 denier. Furthermore, with current fiber technology, if the fibers are too thin, it is difficult to construct a nonwoven fabric that maintains the bulk of the entire nonwoven fabric, so when using the above-mentioned fibers, it is preferable that the fineness is 2 denier or more.

The basis weight may be set in any way as long as f" is 0.8 g-cm3 or more, but considering the covering properties for the absorbent article and the process efficiency when manufacturing the absorbent article, it is 5 to 50.
It is desirable to set it between g/m2.

Further, it is necessary that the formed nonwoven fabric has appropriate hydrophilicity. For example, hydrophilic properties may be imparted to the nonwoven fabric through the use of fibers with hydrophilic surfaces, such as rayon. However, in order to increase absorption speed and suppress stickiness on the surface of the nonwoven fabric and liquid return from the absorbent layer, it is better to have a higher proportion of fibers with a hydrophilic surface and hydrophobic interior. 100% fiber like
The nonwoven fabric is made up of: Fibers whose surface is hydrophilic and whose interior is hydrophobic include, for example, the surface and interface of hydrophobic synthetic fibers such as polyolefin fibers such as polyethylene and polypropylene, polyester fibers, polyamide fibers, and polyacrylonitrile fibers. The surface can be improved by treatment with an activator, chemical surface modification by chemically bonding chemical substances with hydrophilic groups such as monomers or polymers with hydrophilic groups, or physical surface modification such as plasma processing. It can be made hydrophilic. In the chemical surface modification, a chemical substance having a hydrophilic group may be bonded to the fiber surface, or a chemical substance having a hydrophilic group may be bonded to each other and crosslinked to cover the fiber surface. More directly, a skin-core composite fiber may be used in which the skin portion is made of hydrophilic fibers and the core portion is made of hydrophobic fibers. Further, the above-mentioned surface modification of the hydrophobic synthetic fiber may be carried out in the fibrous state before forming the nonwoven fabric, or may be carried out during the process of forming the nonwoven fabric. In these surface hydrophilic states, appropriate hydrophilicity can be set before the liquid permeates, and after the liquid permeates, it falls off with the liquid and the hydrophobic surface is exposed, or the hydrophilicity decreases and the absorption layer from that part is removed. It is most preferable to use a surfactant treatment, which has an excellent effect of suppressing liquid return.

The absorbent article of the present invention is manufactured by covering the lower and side surfaces of the absorbent layer with a leak-proof layer, if necessary, and covering the surface thereof with a nonwoven fabric that satisfies the specific conditions described above.

The materials for the absorbent layer and the leak-proof layer used in the absorbent article of the present invention are not particularly limited, and those used in conventionally known absorbent articles can be used.

〔Example〕

The absorbent article of the present invention can be used for sanitary napkins, postpartum napkins, disposable diapers, cosmetic cotton, etc., but here we will focus on disposable diapers, which are intended for excretory fluids whose volume and viscosity are much larger than those of other products. The present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 17 and Comparative Examples 1 to 9 Absorbent articles were produced from nonwoven fabrics produced using various fibers, compositions, and production methods shown in Tables 1 and 2 by the method below, and their performance was evaluated by the method shown below. The test results are shown in Tables 1 and 2.

<Nonwoven fabric sample> 1 2 A nonwoven fabric sample was manufactured in the following manner.

(1) Comparative Example 1: A commercially available porous water-needled nonwoven fabric was treated with an alkyl phosphate surfactant to impart hydrophilicity.

(2) Comparative Examples 2 to 4: Nonwoven fabrics were peeled off from commercially available paper diapers, and holes were made in each case using the following method.

■Comparative Example 2.3=Diameter 1. A metal pin with a diameter of 5 mm was heated to a higher temperature than the constituent fibers of the nonwoven fabric, and a hole was made by penetrating the nonwoven fabric. At this time, the fibers around the hole are melted by the heated pin.

Comparative Example 4: A metal pin with a diameter of 1.5 mm was heated to a temperature 20° C. lower than the constituent fibers of the nonwoven fabric, and a hole was made by penetrating the nonwoven fabric. At this time, heat was set so that the area around the hole would not melt, and the hole would not be blocked.

(3) Examples 1 to 17, Comparative Examples 5 to 9: Holes were formed at the same time as nonwoven fabrics were produced by the suction heat bond method. That is, a fiber web is placed on a metal net with unevenness, hot air with a temperature lower than the melting point of the constituent fibers is passed from above, and the web on the protrusions is pushed into the recesses, and the parts corresponding to the protrusions correspond to the holes and the recesses. The fibers are distributed so that the portions with holes are non-porous, and then hot air at a temperature higher than the melting point of the constituent fibers is passed through the web to thermally fuse the fibers together to form a nonwoven fabric.

Examples 1 and 2.3 first produced the nonwoven fabric of Example 3,
Set the thickness (sandwich the nonwoven fabric between plates with different clearances and set the thickness to be lower than the melting point of the binder fiber (approximately 50 to 70
``C) Treatment at temperature for a certain period of time) to adjust the average fiber feel distance of Comparative Example 5, Example 1, and .2.3.

In Tables 1 and 2, abbreviations for nonwoven fabric manufacturing methods have the following meanings.

NN: Water needling method SPB Nispun bond method HRB: Heat roll adhesion method CBB: Chemical binder adhesion method 5liB:
Xaction heat bond method <Measurement sample> Using the nonwoven fabric prototyped above, remove the nonwoven fabric from commercially available disposable diapers (product name: Merries, manufactured by Kao ■) and commercially available sanitary napkins (product name: Laurier, manufactured by Kao ■). Instead, articles covered with these nonwoven fabrics were used as absorbent articles intended for disposable diapers and sanitary napkins, respectively.

Test method> (1) Thickness: A pressure plate of 50 mm x 50+ nm is placed on the nonwoven fabric, and the thickness of the nonwoven fabric under a pressure of 2.5 g/cm2 is measured using a dial gauge type thickness meter (manufactured by PEACOCK).

(2) A sample with a width of 50 mm is cut out in a direction perpendicular to the orientation of the strong crab fibers of the nonwoven fabric. Using a tensile tester, the breaking strength is measured when the sample is pulled in a direction perpendicular to the fiber orientation with a distance between chucks of 100 mm.

(3) Surface liquid flow: ■ Paper diaper assumption = 3 g of test liquid is discharged at 1 g/sec from 1 cm above onto the sample surface inclined at 45 degrees.

Measure the length of flow of the test liquid on the surface of the nonwoven fabric. The following three types of test liquids were used.

A: A low viscosity liquid with a viscosity of l c, p, urine is assumed.

B...Viscosity 250 made by dispersing flour in water
Artificial soft stool of c, p, C... viscosity 10c made by dispersing flour in water,
Artificial diarrhea stool of p ■ Sanitary napkin assumption: Drop the test liquid at 10 g/min from 1 cm above onto the sample surface inclined at 45 degrees, and drop it on the nonwoven fabric surface from the dropping point to the point where it is absorbed into the sample. The distance traveled was measured. The following three types of test liquids were used.

A...Low viscosity liquid with viscosity toc, p. Assuming low viscosity menstrual blood.

B...Viscosity 350c of test liquid A thickened with CMC,
p.

High viscosity liquid. I assumed lochia.

5 6 In all cases, the shorter the surface liquid flow, the more the flow of excretory liquid will be suppressed.
Indicates high leak prevention ability against side leaks.

(4) Return amount: ■ Paper diaper assumption: 150 g of test liquid A was injected into the sample, pressurized after a certain period of time, and the amount of test liquid returned from the inside through the nonwoven fabric was measured.

■ Assumed sanitary napkin: Test solution A 1. Og was injected into the sample, pressurized after a certain period of time, and the amount of test liquid returning from the inside through the nonwoven fabric was measured.

The smaller the amount of return, the less sticky it will be on the surface.
Easy to use and has excellent wiping effect.

(5) Shedding of fluff: When the surface of the nonwoven fabric was rubbed with a load (15 g/cm2) wrapped around a sponge, the amount of fibers that came off from the nonwoven fabric and landed on the sponge (=j) was evaluated.

Evaluation Criteria: Grade 3: Almost no fibers are observed, Grade 2: Fibers are noticeable, but there are no fiber balls. Grade 1: There is significant fiber loss, and there are many fiber beads (6) Texture : Sensory evaluation was performed on the softness and feel of the surface of the nonwoven fabric.

Grade 3: Soft, feels good on the skin.

Grade 2: Slightly hard and rough, but usable.

Grade 1: Hard, rough, and unusable.

(7) Average interfiber distance and f″: Measure F, L, α4+ Di+ li, and calculate from the previously derived 2.

Although the fiber length of spunbond nonwoven fabric is almost infinite, considering the structure of the nonwoven fabric, it was assumed that fibers with a fiber length of 5.1 cm were connected, and calculations were made using l1 = 5.1.

(8) Thickness ratio around pores: Observe the cross section of the nonwoven fabric containing pores with a microscope, measure the maximum thickness of the non-pore part and the minimum thickness L2 around the pores, and calculate by the following formula.

Thickness ratio around the hole = 100 XL2/Ll (9) Opening ratio/
Pore diameter: Measured using an image analysis device.

■ Model name: Image Command 4198
■ Manufacturer: Nippon Avionics Co., Ltd. ■ Measurement of porosity: Measure the dark and light areas of the black mount. When the sample nonwoven fabric is placed on the black mount, the pixel portions of the black mount that indicate the shading areas correspond to the holes. The open area ratio P was calculated using the following formula from the number of pixels X in the light and shade region corresponding to the hole portion and the number A of pixels in the entire image processing area of the nonwoven fabric sample.

P-100XX/A (%) ■ Measurement of pore diameter: When image processing is performed to binarize the shading of the shading area corresponding to the pore and the other shading areas, an image in which pores are distributed in an island shape is created. can be seen. Number of islands (holes) N
and calculate the average pore area a by the following calculation: a=c
-X/N (C is known hole area/number of pixels within known hole area)
In the conventional nonwoven fabric shown in FIG. 1, even if the nonwoven fabric strength is high, the average interfiber distance is small, and as a result, f9 is small. Therefore, the absorbency of low viscosity liquids (test liquid A) is good, but the permeability of high viscosity liquids (test liquids B and C) is
The effect of the holes is not fully utilized. Depending on the hole-opening method, the fibers around the hole may melt (Comparative Example 2゜3), or the area around the hole may become hard (Comparative Example 4), and the thickness around the hole may decrease.
The texture of the skin is significantly reduced.

As shown in Examples 1 to 4, if the average inter-fiber distance is 60μ or more and f" is 0.8 g-cm3 or more, the nonwoven fabric strength and the average inter-fiber distance are simultaneously large. When these conditions are met , the non-porous area is not clogged with high viscosity liquid and the pores are fully effective.

As in Comparative Examples 5 and 6.8, when the pore area is less than 1.5 mm'' or the pore size is less than 5%, the effect of the pores on the permeability of high viscosity liquids is not expressed. On the other hand, if the pore area is too large or the pore size is too large as in Comparative Examples 7 and 9, the absorbent material may come into direct contact with the skin and become sticky or have a poor texture. This causes problems such as the fluff coming off and the strength decreasing.

As shown in Examples 1 to 17, the above (
Nonwoven fabrics that meet all of the conditions shown in 1) to (6) are strong and
The distance between the fibers is appropriate, the effect of the pores is effectively exhibited, and an absorbent article with a well-balanced texture, smooth feel, etc. can be constructed.

Claims (6)

[Claims] 1. An absorbent article characterized by using a nonwoven fabric that satisfies all of the conditions shown in (1) to (6) below as a surface material. (1) At least the excretory liquid permeable portion has a large number of holes. (2) The average interfiber distance in the non-pore portion is 60μ or more. (3) The ratio f^* between the strength of the nonwoven fabric and the fiber number density expressed by the following formula (I) is 0.8 g·cm^3 or more. F^*f=F/(N/V)・(g・cm^3)...(
I ) (In the formula, F: Tensile strength in the direction perpendicular to the fiber orientation of the nonwoven fabric (g) V: Volume of the nonwoven fabric (cm^3) N: Indicates the number of fibers in the nonwoven fabric.) (4) The average pore area is 1.5 to 20 mm^2/piece. (5) The porosity is 5 to 50%. (6) The bonding point density in the non-porous portion is almost uniform.